Elevators generally comprise a holding brake, which is used to keep the elevator car in its position when the car is stopped at a floor level. This same brake is often used also as an emergency brake as required by elevator regulations, which brake is switched on in exceptional situations, such as during an electricity power cut. A drum brake or a disc brake, for example, can be used as a brake.
Conventionally a drum brake is used in elevators, which drum brake comprises at least an active part provided with a brake pad and with an actuator moving the brake pad, and a brake drum connected to the rotor of the hoisting motor in the hoisting machine and rotating along with said rotor, on the outer rim of which brake drum is a braking surface. The drum brake of an elevator generally operates such that when the brake is closed, the spring comprised in the active part of the brake presses the brake shoe and the brake pad connected to it against the braking surface of the brake drum, in which case the elevator car stays in its position. During a run, current is connected to the electromagnet of the brake and the magnet pulls the brake shoe and the brake pad off the braking surface of the brake drum, in which case the brake is open and the elevator car can move up or down in the elevator hoistway. The brake implementation of an elevator can be e.g. such that the implementation comprises two brakes functioning as the active part, which brakes are disposed outside the rim of the brake drum on opposite sides of the rim of the brake drum to each other as viewed from the front in the direction of the axis of rotation of the brake drum.
The force acting on the brake drum of a drum brake when the brake engages is quite large, owing to which the brake wheel absorbs a lot of kinetic energy. This produces a loud noise when the brake pad hits against the brake drum. To solve this problem the aim has been for the air gap between the brake pad and the brake drum to be as small as possible. In this case the brake pad does not have time to achieve very great speed and kinetic energy when it hits the brake drum, as a result of which the impact is more subdued. An air gap that is small enough is, however, difficult to implement and also to adjust, and this type of solution results in a very fragile structure and also in extremely precise manufacturing tolerances. Another problem is that brake pads wear over the course of time, in which case the air gap between the brake pad and the brake drum increases. When the air gap between the brake pad and the brake drum increases, the movement of the brake pad also increases and therefore the noise caused by the operation of the brake becomes louder. The air gap of the electromagnet of the brake also increases as the brake pad wears. As the air gap increases, the attractive force produced by the electromagnet decreases, in which case the operation of the brake slows down and the brake does not even open properly.
Nowadays the adjustment and installation of machinery brakes are performed on the production line of the hoisting machine manually. It would be advantageous to find a solution wherein the adjustment/installation of machinery brakes could be at least partly automated. In addition, it would be advantageous to find a simpler solution than the known one for adjusting the air gap between the brake pad and the brake drum for reducing the noise nuisance caused by the wearing of a brake pad.